Electric steam boiler



June 23, 1925. 1,543,514

A. N. TIS

ELECTRIC STEAM BOILEH Filed May 16, 1924 Patented June 2x3, 1925.

UNITED STATES PATENT OFFICE.

ALBERT N. OTIS, 0F SCHENECTADY, NEW'YOBX, ASSIGNOB T0 GENERAL ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

ELECTRIC STEAM BOILEB.

Application led lay 16, 1924. Serial lo. 713,881.

To all yzcliontz' may concer/n.'

Be it known that I, ALBERT N. Oris, a. citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Electric Steam Boilers, of which the following is a specification.

The present invention relates to electric steam boilers of the type wherein the water is heated by electric current flowing through the water between electrodes submerged in the water, and especially to such boilers when heated by three-phase alternating current.

In connection with suc-h boilers it is known that a certain current density must not be exceeded if smooth satisfactory operation is to be obtained for if the current density becomes too great it appears to result in the formation of arcs in the water and givesrise to noisy, erratic operation. In providing electrodes for steam boilers,

therefore, the size of the electrodes has been largely influenced by the quant-ity of current required for full load operation, the electrodes being chosen of such size that with full load the permissible current density will not be exceeded. However, in actual practice considerable diiculty has n experienced with electrodes which according'to calculations had ample surface to carry the current required for the intended rating of the boiler and this I have found is due to the fact that with the ordinary types of electrodes heretofore used the current does not distribute itself evenly over the surface of the electrodes but tends to concentrate at certain parts of the electrodes whereby at such parts the maximum permissible current density is exceeded.

The object of my present invention is to provide an improved'electrode construction and arrangement for three phase alternating current electric boilers wherein the current will be distributed evenly over all parts of the electrodes, and for a consideration of what I believe to be novel and my invention, attention is directed to the accompany ing description and the claims appended thereto.

In the drawing, Fig. 1 is a side elevation partly in section of a boiler embodying my invention, and Fig. 2 isia sectional view taken on the line 2-2, Fig. 1.

Referring ,to the drawing, 1 indicates the outer shell or casing of an electric boiler and 2 an inner shell or basket which is supported on a Suitable frame 3 in spaced relation to the bottom of outer shell `1. The bottom of inner shell 2 is indicated at 2. Inner shell 2 is provided with spaced holes 4 in its side walls through which water supplied to inner shell 2 may run back into the bottom of outer shell 1. Projecting in through the top of casing 1 are three spaced conductors 5 surrounded by suitable insulators 6, and carrying at their inner ends electrodes 7 which depend into inner shell 2. Water is supplied from the bottom of outer shell 1 to the bottom of inner shell or basket 2 by a pump 8 which has its suction side connected b a pipe 9 to the. lower end of shell 1 and its discharge side connected b f a ipe 10 to a transverse chamber 11 at t e ttom of shell or basket 2. Chamber 11- communicates with the interior of shell 2 through a row of holes 12 in the bottom 2* of the shell. The power input to the boiler is regulated by the hei ht of the water level in inner shell or bas et 2 and this in turn is controlled by the rate at which pump 8 supplies water to it. As is well understood, the input to the boiler varies directly with the depth to which the electrodes are submerged. At 13 is indicated the steam discharge conduit of the boiler.

In operation, the three conductors are connected to the three phases of a source of three-phase alternating current and the inner shell of basket 2 is grounded to form the neutral point of the system. vCurrent then flows through the water from one electrode to another and also from the electrodes to the inner shell 2.

The electric boiler 'ust described is of the general type of t at disclosed in the patent to Merrill and Winne No. 1,462,350, patented July 17, 1923, and is to be taken as typical of any suitable electric boiler, it being understood as will appear more fully hereinafter that my invention is applicable to electric boilers of any suitable t)'Pe- Now according to my invention I provide electrodes of substantial triangular shape in cross section, each having an outer face 14 and two inner faces 15, and I make the outer faces 14 curved on the same curvature as the side wall of inner shell 2 and the inner faces 15 flat and extending at such an angle that the faces 15 of adjacent electrodes are parallel to each other. I then so position the electrodes in the shell 2 that the distance between the outer face 14 of any electrode and the side wall of shell 2 is to the distance between adjacent electrode faces 15 as 1 is to 1/3. Or, in other Words, the distance a between electrode faces 15 is approximately 1.73 times the distance Z) between faces 14: and shell 2. This is done so that the resistances of the various current paths will bear the same proportional relation to the potential impressed upon them, for as is known, in a three-phase alternating current system having a grounded neutral the potential between the phases is equal to times the potential between each phase and the neutral point of the system.

It will thus be seen with my improved electrode arrangement that all adjacent points of the inner faces 15 of the electrodes are the same distance apart so that the resistance between electrodes at all points is the same, and likewise that all parts of outer faces 14 of the electrodes are the same distance from shell 2 so that here again the resistance at all points iis the same, and in addition to this, that the electrodes are so spaced with relation to each other and with relation to the shell that the resistances of the respective paths between the electrodes themselves and between the electrodes and the shell bear the same relation to the Ipotentials between these parts. By this means I have found that I obtain an even distribution of the current at all points throughout the liquid in the boiler.

As an example of the results accomplished by my invention, in one case in a boiler provided with round electrodes it was found uite impossible to operate it at its rated ull load or even n'ear its rated capacity, the operation at such times being noisy and accompanied by constant fluctuations of the ammeters in the power circuit. In the particular case the boiler was rated at 5500 kw. but even at 3000 kw. the operation was extremely unsteady. The electrodes in this boiler were replaced by electrodes embodying my invention and Iwas then enabled without difficulty and without noise or fluctuations of the ammeters to run the boiler at its full rated input of 5500 kw.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In a three-phase electric boiler, the combination of a shell which forms a neutral of the system, and electrodes in said shell, said electrodes being triangular in shape and having curved outer faces which conform to the curvature of the shell and flat inner faces which stand parallel to each other.

2. In a three-phase electric boiler, the combination of a shell which forms a neutral of the system, and electrodes in said shell, said electrodes being triangular in shape and having curved outer faces which conform to the curvature of the shell and flat inner faces which stand parallel to each other, said flat faces being spaced apart a distance equal approximately to 1.73 times the distance between the curved outer faces and the shell.

3. An electric boiler for operation with three-phase alternating current and comprising a shell and electrodes which project into the shell, characterized by the fact that the electrodes are so arran ed in the shell that the distance between tiem is approxilnately 1.73 times the distance between the electrodes and the shell.

4. An electrode for use in an electric boiler, said electrode being of trian lar shape in cross section and provided with a curved outer surface and flat inner surfaces.

In witness whereof, I have hereunto set my hand this 14th day of Marly, 1924.

ALBER N. OTIS. 

